Vibratory meters, such as Coriolis flow meters, typically include a sensor assembly with one or more vibratory elements. The vibratory elements may be flow tubes, tuning forks, or the like, that carry or are suspended in a material to be measured. A driver vibrates the one or more vibratory elements to induce a response by the sensor assembly. The response by the sensor assembly is used to determine properties of the material.
To measure the response, the sensor assembly can include two or more pickoff sensors that can be employed to determine a spatiotemporal relationship between two or more positions on the vibratory element. For example, a first pickoff sensor may be at a first position and a second pickoff sensor may be at a second position. Each of the pickoff sensors may measure a spatiotemporal property such as, for example, velocity, displacement, or acceleration. The measurements from the two or more sensors can be combined to determine the spatiotemporal relationship between the two or more positions. For example, signals from the two or more sensors may be subtracted to determine a phase difference between the two or more positions.
The spatiotemporal relationship of the two or more positions may correspond to the properties of the material. For example, in Coriolis flow meters, the phase difference between the first and second position may be correlated with the flow rate of the fluid flowing through a vibrating tube. By determining the phase difference between the two or more positions on the vibrating tube, the flow rate can be determined. Other properties may also be determined and other spatiotemporal relationships can be employed.
Although the two or more sensors at the two or more locations can be employed to determine the spatiotemporal relationship between the two or more positions, it may be advantageous to use alternative designs that do not employ the two or more sensors. For example, it may be advantageous to employ a single sensor that measures the spatiotemporal relationship. Advantages can include simpler vibratory sensor assembly design and more reliable measurements. Accordingly, there is a need for measuring a spatiotemporal relationship between two or more positions of a vibratory element.